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Monthly Archives: January 2015

Looking back over my outreach activities since I moved to Australia in 2008, I seem to have reached more people than I thought. For the three years I was in Perth I ran the outreach activities of our research group, organising many activities over the International Year of Astronomy in 2009 and beyond, and participating in many activities organised by other entities. In 2011 my contract ended and I moved to take up a job in the Netherlands. In a country where you don’t speak the language, direct outreach is much more difficult, but I did continue with the podcasting, radio work, and other occasional bits of science writing (not counted in the numbers here, it’s much harder to quantify these without the download statistics or listener figures). In mid-2013 I moved back to the UK and have been running my own outreach activities independently, doing many youth groups, SciBArs, schools, festivals, and other assorted public talks and lectures. Adding everything up (exact numbers where known, estimates otherwise), I have personally reached over 10,000 people. Not counting the years I was in the Netherlands, that is an average of over 2,000 people a year, in my spare time. Not too shabby.

Never mind the new year fireworks, the start of 2015 happened with an even bigger bang, at least if you happened to be in Romania, Moldova or the Ukraine. The early hours of January 7th saw a massive fireball over the region, culminating in an explosion loud enough to wake people, and causing many to call the emergency services to report the event. In Romania reports of sightings have come in from across the country, putting the time of the explosion at 3:05 EET (01:05 UT), with people hearing the explosion in the counties of Buzau, Vrancea and Covasna.

So far over 50 recordings and eye witness reports have been collected by the IMO, many from surveillance cameras recording sudden brightening of whatever outside area was being monitored. A compilation of videos of the event, as recorded by security cameras, can be viewed on youtube at https://www.youtube.com/watch?v=WjS8GHu_0ZM. The map below shows the location of the reports received so far, red dots are from surveillance cameras, the blue markers are visual reports from witnesses, and the green dots are reports from those who heard the terminal explosion.

Fireballs are exceptionally bright events which happen when a meteoroid passes through the atmosphere. Stand outside on any clear night for more than a few minutes, and you will see a meteor somewhere in the sky. Meteors are caused by small pieces of rock, generally less than a millimetre in size. They range in brightness from too faint to be seen with the naked eye, right up to brighter than the full moon. The majority of meteors are at the faint end of this scale, while fireball events like this one are at the extreme upper end of this range.

The reports from Romania of the January 7th fireball put the maximum apparent magnitude of -16, brighter than the full Moon (-13). For comparison, the Sun has an apparent magnitude of -26, the brightest star in the night sky, Sirius, has an apparent magnitude of -1.4, and the human eye is capable of seeing as faint as magnitude +6 under good observing conditions from a dark site.

The magnitude scale is logarithmic; a star with magnitude +1 is actually 2.512 times brighter than a star with magnitude +2. The apparent magnitude above which a meteor is considered a fireball is somewhat arbitrary, with different publications defining it by different numbers. Roughly one in 1,200 meteors is brighter than magnitude -5, while only one on 12,000 meteors reaches magnitude -8 or brighter, so fireball events like this one are rare.

Almost all small meteoroids disintegrate during their passage through the atmosphere. But sometimes, very bright fireball events can result in a meteorite fall, where the meteoroid (or parts of it, in the case of an explosion) reaches the ground. If this happens, reports from people who saw the event are vital in determining the likely location of the debris.

So far, information on the event is sparse. The explosion appears to have occurred at a height of roughly 55 kilometres and it is likely that the meteoroid completely disintegrated. Whether a fall occurs or not, the details of events like this can only be determined from combining the information from many eyewitness reports. If you see a bright fireball event like this, you can help researchers by reporting what you saw in as much detail as possible. You can find further information on meteors and other related events, and advice on how to observe and report them, visit the IMO website at http://www.imo.net/

January 4th sees the peak of the annual Quadrantid meteor shower. The Quadrantids is often a poorly-observed event due to the weather in the northern hemisphere at this time of year, and 2015 is worse than usual as the peak of the shower coincides with the date of the full Moon. Caused by the Earth passing through streams of leftover debris from comets or asteroids, meteors showers are conventionally named after the constellation from which they appear to radiate. The Quadrantids, however, are named after an abandoned constellation named Quadrans Muralis, the mural quadrant, now a part of Boötes, the Herdsman. Boötes is home to the star Arcturus, a giant star and the fourth brightest star in the sky, although the rest of the stars in the constellation are much fainter. The radiant of the Quadrantids is located in the north of the constellation, close to the tail of Ursa Major, the Great Bear (see the image below).

Visible only at northern latitudes, the shower is active between December 28th and January 12th, although with relatively low numbers either side of the peak on January 4th. At the peak of the shower, early in the morning of January 4th, models predict that there will be up to 120 meteors per hour when observing under ideal conditions. In practice, the numbers observed will generally be lower than the predicted rate (also known as the ZHR, Zenith Hourly Rate) because observing condition are rarely ideal. Despite being one of the more active showers of the year, the debris which forms the Quadrantids results in meteors which are fainter on average than many of the more well-known showers and, with the first full Moon of 2015 occurring on January 5th, conditions this year are far from ideal for visual observing. This shower is unusual in that the parent body, the comet or asteroid which left the debris which gives us this particular light show, remained somewhat uncertain for many years, despite the high activity of the shower. There is more than one candidate object, with many specialists arguing that the asteroid 2003 EH1 is the likely source, but there are other candidates, and the evolution of the orbit makes identification more difficult.

The approximate position of the radiant of the Quadrantid meteor shower (image made with stellarium)

My view: this year I saw a big fat zero. Last night was also the annual visit to Macclesfield Astronomical Society of the historian of science Dr Allan Chapman; the subject of his lecture this year was the astronomer and mathematician Kepler. Driving home in thick fog at 10:30pm, I gave up plans to do any observing as I could barely even make out the location of the Moon. Another excellent reason to fix up another radio receiver to replace the now non-functional Jodrell Bank Observatory Meteor Detector…